Electrical contact device



Dec. 20, 1949 c. H. BROOKS ELECTRICAL CONTACT DEVICE 2 Sheets-Sheet 1 Filed June 10, 1948 Dec. 2G,` 1949 c. H. BRooKs 2,491,603

ELECTRICAL CONTACT DEVICE Filed June l0, 1948 2 Sheets-Sheet 2 v T1 N N 5 C 1 "i A m. u r, ii L QQ y im N W @my 'W WS N.

Patented ec. 20, 1949 ELECTRICALy CONTACT DEVICE Charles Brooks,- Milan, Ill..,'assignorV to"vBear.-. Manufacturing Company,- Rock-lsland, Ill., a'y

corporation of Delaware ApmicatinJune 10'; isialseriai'nmezzo 4 claims.' (cl. 2in-152)4 This, invention .relatesgtos improvements in Ia contact device forza-machine forltesting the 'dynamic balance of rotating bodies,` and refers particularlyzto a device for making and breaking an electriccircuitrinresponseto the unbalanced conditionof arotating body..y

In testingi thedynamiczbalance of rotating bodies, one;form .ofbalance testing machine in` dicates aconditioniof unbalance-of a body being 'Y rotated by lempl'oyingzthe displacement of Veccentricity of motion of the .rotating body to make and break a: primaryy electric circuit inductively coupled-to a high tension; circuit,'the high tension circuit,1upon,the -breakingoi-lth primary circuit;

unbalancer of 'the body.llv Such a machine is shown 4 generally s ina. United States Patentv4 Number 2,412,473 to E. L; Schnoebelen'.

tating 'bodyl andis responsive to eccentric movementfof theunbalaneedl'body, and the othen carriedbyrthe iframe-ofthe?machina* In view of' the fact that thefdegree of movement ofthe cradle in'response to unbalance ofthe body is proportional to the degree of iunbalance, the contactf mounted upon 'the'- 'irai'ne is manually adjustable" toward or 'awayffromfthelother Contact so as toA17 compensate for! different degrees foim'ovement ofV the cradle.'v In addition', the `contact carriedbyf the cradleI -is -'spring#pressedfk so that excessive swings of the cradle'r will not damage-th contacts.

In order to secure the 'exact-'point' of imbalance upon the-body','itisnecessaryl when operating .the

machine to back oit the adjustable contact until ofthe cradlel. i Otherwise 'the rcradle contact may 34 the 'contacts barely touchatfth-makimum swing dwell in contact with'A- the "iframe contact until after the maximum point of unbalance has been passed. Thislisja likely'occasicn'ior human error operator.4

As a feature'of'the present invention, two con' tactsv are employed forth'et making'v and breaking of the primarycircuit, both contactsr beingm'ovable;y whereby b1"eaking'off the primary circuit automatically occurs at the instant reversalA of movement of the :cradle takesplace thus auto-f matically'indicating the exact point of unbalanee' ofthe body, vwith the necessity'for no manual ad, justmentsf the contacts.v`

Other? l*objects and advantages" ofthe 'present' invention'wl be apparent-from the accompany ingrdrawings 'and following detailed description-i Fig;- v1 is an elevational view? of one cradle ein#` ploye'diin a conventional balanc'etesting machine.

-Fig.'2 is an'enla'rged detail view of a porti'cno'? the cradle, parts; ofthe Contact mechanism being*A shown-in section.` I y Fig. 3 isa sectional-view taken-on line EY3;3 'off' Fig; 2. The. present 'inventiony `is vparticula-rl-y adaptable* for use with balance' testing machines i"of lthe typecomprising airamefa pair? oi swingable cradles@ carried by theiram'e, 'the-body to be testedjbeing rotatably carrie'djby a 'shaft` journalled uponsaidf cradles,v` said shaft 4beingvv 1Vrotated by 'a motor or 5 othersuitable prime fmcver. Associated with' each i ofthe cradlesis a'make and-'break mechanism which is` connected in fthe'primary circuit 'of the f usual spark coil whereby swingable movement of the cradles energizes the-secondary` circuit of the spark coil'and gives' an indication ofthe condition of imbalance fof the rotating body. Such aj balance testing machine is shown and'describ'ed in theifabove" identied Letters Patent 'Number 2,412,473. A.

Referring *particularly tothe drawings, I indi#A j cateslthe main frame vof la'f`balaI1ce testingv ma-3,;` chine, 'suchas hereinbeforedescribed. A pair of jj standardslf onepf which Vis illustrated', are mounteduponthe/frame I and secured thereto by', means of bolts or the like 3. kEach of the standards 2v has'-'apair of tdwer members (l, the 111913611.. ends of `which" extend inwardly toward each c`) i', he"r.'` A cradle A5 is support'edby the tower members' 4; said""cadle comprising' `a transverse supportV 6 pivota-lly"securedY 'atj its opposite endsto links 1. f Each'of-trifunksi is pivotauy `carried 'by the' uppeririturnedends of the towers 4,. A bearing 8; is carried 'byeach ofjfthe'supports 6 of cradles 5j" being adapted tocarry shaft' 9 upon which rbody l mfh'body lWhose 'balance is to be testedisz mc'iuntedfl t Thusiar described the machine isconventional]` andcomprises;v per"'s e,jno part of the presentim venti Inthe oper'ationyoi this device, theshaft 9 is'rtated at a speed, depending' upon the'A body beiri'g'tested, which *may range from about 40D j revolutions per minute': to as' high 'as` 2500 `revoluV tion per' mi n ute.` If the body is in a stateof unbal'ancefthe unbalancewill cause supports 6 tof oscillate horizontally;l as viewedv in Fig. '1, the eX tent offthev maximum swing' being substantially] proportional to the degreeV of unbalance-of the bOdy. l

TheAly present'invention contemplates a set ofKA 3 make and break contacts and associated mechanism which will now be described.

A plate II is secured by means of bolts I2 or the like, to the support 6 adjacent one end thereof. A plate I3 of insulating material such as Bakelite, fibre board or the like is carried by plate II, being secured thereto by screws I4. The insulating plate I3 extends beneath plate II and carries a contact point I5 which is secured in place by nuts I6, the arrangement being such that a limited degree of adjustability is provided for point I5.

A sleeve I1 is formed integral with plate II and is provided with an elongated aperture I3 coaxial with point I5. A plunger I9 is slidably positioned in sleeve I1, said plunger, at its end adjacent point I5, carrying a contact point 20, the Shank of which is threadedly engaged in the end of the plunger I9. Nut 2| is rigidly positioned upon the shank of the point and affords means for screwing said shank into the plunger. Nut 22 is a stop which functions to limit movement of plunger Iii to the left, as viewed in Figs. l and 2.

An inverted J-shaped bracket 23 is rigidly mounted upon the standard 2, said bracket carrying a pin 24 upon which a weight 25 is pivoted. The weight 25 is provided with a sleeve portion 25, above the pivot pin 24, through which a rod 21 is slidably positioned. Rod 21 is rigidly secured to plunger I9 at its opposite end and is adapted to move therewith. It will be noted that the center of gravity of weight 25 is oiset from the pivot pin 24 and, hence, said weight exerts a moment of force about said pivot pin tending to rotate said weight in a clockwise direction about the pin. This force is resisted by contact of the sleeve 25 upon rod 21 thereby establishing a frictional connection between rod 21 and weight 25.

in operation, body IU is mounted upon shaft 9 and said shaft is rotated at a suitable speed. If the body I0 is unbalanced statically or dynamically the rotation thereof will cause the cradle 5 to swing. Contact point I5 is connected to one side of the primary circuit and point 2D is connected to the other side thereof, the latter being grounded upon the machine. The electrical connections are not shown inasmuch as they are well known in the art, with particular reference tol Patent Number 2,412,473 hereinbefore mentioned.

It can readily be seen that as the cradle swings plate Il moves therewith, and point I5 is rigidly carried by said plate. Point 20 also moves generally with the movement of plate II, there being, however, a degree of limited movement of said point with respect to plate I I and, hence, with respect to contact point I5. Referring particularly to Figs. l and 2, when cradle 5 swings to the left, contact point I5 makes Contact with contact point 20 since the frictional connection between rod 21 and weight 25 frictionally resists relative motion between rod 21 and said weight. Hence, plunger I9 slides within sleeve I1 until points I5 and 2B make contact. Thereafter, motion to the left by cradle 5 moves both pointsv I5 and 2E] to the left. The primary circuit is thus completed. However, when cradle 5 reaches the end of its leftwise swing (depending in extent by the magnitude of unbalance of the body) and then reverses its motion, rod 21 and, hence, plunger i9 and contact point 20 remain stationary while contact point I5 moves away to the right from contact point 20. This retarding of movement of rod 21 is caused by its frictional connection with weight 25. Thus, the primary circuit is broken at the instant of reversal of movement of the cradle and high tension current is set up in the secondary circuit (not shown) and an indication is given, the indication showing that the point of unbalance of the body ID has just passed the left horizontal. In this manner the point of greatest unbalance of the body is ascertained.

As the cradle 5 continues its swing to the right, nut 22 eventually contacts the end of sleeve I1 and rod 21, plunger I9 and contact point 20 are carried to the right, the latter being carried in spaced relationship, however, with respect to contact point I5. At the limit of the swing of the cradle 5 to the right and at the commencement of its swing to the left, contact point 20 again remains stationary until contact point I5 has again moved into contact therewith and the cycle is thus completed.

It can readily be seen that the arrangement hereinbefore described comprises an automatic means for selecting the substantially exact point oi greatest unbalance of the body at a predetermined phase of its rotation at which to break the primary circuit and produce an indicating signal in the secondary circuit. It can also be seen that this automatic means of selection is substantially independent of the magnitude of unbalance of the body except for extremely small degrees of unbalance, that is, when the body I0 is substantially in balance. Hence, the testing of unbalance of a body can be made quickly Without the necessity of manually adjusting the position of one of the contact points which is a relatively slow process.

In addition, in ascertaining the position of unbalance of a body by manually adjusting one of the contact points implies that the make and break of the circuit occurs almost instantaneously. At high speeds of rotation the period of make may not be suicient to satisfy the time constant of the primary circuit and, hence, a weak or faulty secondary discharge may result. In the present invention, however, the period of make comprises substantially one-half cycle of rotation of the body and at all practical operating speeds a strong secondary discharge will result.

For simplicity and clarity of explanation, only one cradle is illustrated and described. It is to be understood, however, that two cradles are contemplated in the complete machine and a make and break mechanism such as herein described is mounted upon each, both being identical and separately operated, as contemplated in the mentioned Patent Number 2,412,473.

I claim as my invention:

l. A device for making and breaking an electric circuit in response to the swinging movement of a body which comprises, a frame, a cradle swingably mounted upon said frame, an electrical contact point rigidly carried by said cradle, a rod yieldably secured by friction to said frame, a lost motion connection between said rod and said cradle, and an electrical contact point carried by said rod in proximity to said first mentioned contact point whereby reversal of motion of said cradle makes and breaks the contact of said contact points.

2. A device for making and breaking an electric circuit in response to the swinging movement of a body which comprises, a frame, a cradle swingably mounted upon said frame, an electrical contact point rigidly carried by said cradle, a rod yieldably secured by friction to said frame, a sleeve carried by said cradle, a plunger positioned in said sleeve and having limited slidable movement therein, said plunger being connected at one end to said rod, a contact point carried at the opposite end of said plunger in proximity to said rst mentioned contact point whereby reversal of motion of said cradle causes motion of said plunger in said sleeve to make and break contact of .said contact points.

S. A device for making and breaking an electric circuit in response to the swinging movement of a body which comprises, a frame, a cradle swingably mounted upon said frame, an electrical contact point rigidly carried by said cradle, an eccentrically mounted weight pivotally secured to said frame, a sleeve carried by said Weight, a rod slidab-ly positioned in said sleeve to hold the center of gravity of said weight offset with respect to the pivot point of said weight whereby to yieldably secure said rod by friction to said frame, a

lost motion connection between said rod and said cradle, and an electrical contact point carried by said rod in proximity to said first mentioned contact point whereby reversal of motion of said cradle makes and breaks the contact of said contact points.

4. A device for making and breaking an electric circuit in response to the swinging movement o a body which comprises, a frame, a cradle swingably mounted upon said fra-me, an electrical contact point rigidly carried by said cradle, an eccentrically mounted weight pivotally secured to said frame, a sleeve carried by said weight, a rod slidably positioned in said sleeve to hold the center of gravity of said weight offset with respect to the pivot point or said weight whereby to yieldably secure said rod by friction to said frame, a sleeve carried by said cradle, a plunger positioned in said sleeve and having limited slidable move-- ment therein, said plunger being connected at one end to said rod, a Contact point carried at the opposite end of said plunger in proximity to said irst mentioned contact point whereby reversal of motion of said cradle causes motion of said plunger in said sleeve to make and break contact of said Contact points.

CHARLES H. BROOK-S.

REFERENCES CITED The following references are of record ln the le of this patent:

UNITED STATES PATENTS Number Name Date 336,303 Christensen Nov. 20, 1906 1,401,991 Lehr Jan. 3, 1922 2,005,122 Young et al June 18, 1935 2,170,900 Jandus et al. Aug. 29, 1939 2,349,530 Weaver et al May 23, 1944 2,392,477 Holm Jan. 8, 1946 

